What's the point of a face mask?

I seriously can't understand why face masks are necessary. Isn't the time a face mask is on too short to have a real effect? Isn't it better to use these ingredients in a face cream where they stay longer? Are there any proven benefits of face masks? Is it really necessary to use face masks weekly if you want to have good skin?

I live in Korea and I have used many of those masks (they often give away free samples when you buy something and I have bought a lot others, they even have hand and foot masks!!) and honestly, I haven't noticed any difference in my skin. I tried clay masks when I was a teenager hoping they will help me with acne but they had the opposite effect and I had a huge breakout I hadn't experienced before. But maybe some face masks really help? I don't know, so I'm asking here.

I think this depends on the mask. An enzyme mask works well to exfoliate the epidermis and the contact time required is usually 5 - 15 minutes, I usually follow this with a hydrating/soothing mask in a thick layer, whether this does anything to actually hydrate the skin, I'm not sure; anecdotally it does seem to reduce redness, sooth & calm the skin faster than going straight to serums/moisturizer but I don't have any supporting data for this. Generally if you want other benefits (lightening/brightening, vitamins, etc) you're best using a serum regularly.